Current ceiling lamps are mounted to ceilings or walls, which not only are for lighting but also play an important role in decoration to indoor environment on the other hand, therefore, appearance requirement for the ceiling lamps is very high on the market; however, because of unreasonable design of the lamps of the prior art, decorative effect of the lamps have been greatly reduced, which cannot meet ultrathin and ultralight requirement demanded by the market. Therefore, it is necessary to provide an ultrathin lamp.